iMac 21.5" 2009 Backlight/Brightness issue

Hello, My name is Rod.

I’m a Mac technician and I’ve been having some issues with an iMac 21.5” 2009.

The main issue is that the brightness/backlight at first came and went randomly. Sometimes I unplugged the power cable for several minutes and then when turned on the iMac the brightness/backlight came on.

But for example, if the iMac went to sleep mode sometimes the backlight simply didn´t came back on again.

So I proceded to replace the inverter board. That actually solved the problem for like a week or so. Now the problem is worse since there’s no backlight at all not even when I unplugged the power cable for a day or two. So I proceded to replace de flex cable that connects the inverter board to the LCD, no luck. Still no backlight.

But if a take my iPhone “flash” and put it right in front of the LCD I can actually see the image of the system in the background. So that means it’s not an LCD or video card problem. I managed to pinpoint the cursor using the iPhone flash technique and went to brightness options and turned the bar all the way up. No luck.

So, is there something else that could be causing the backlight problem?

Any suggestions? I look forward for any help.

Thanks in advance.